Welcome to #AGA2024!! Here we will share some bits, pieces, and anecdotes from this year’s presidential symposium! Our president Beth Shapiro put together a great list of speakers and we have many excellent poster presenters.
Day 3: Afternoon Talks
Aryn Wilder, Fitness benefits of genetic rescue despite chromosomal differences in an endangered pocket mouse
Aryn works as part of the San Diego Zoo Wildlife Alliance, specifically in conservation genetics. She investigates the utility of genetic rescue to relieve inbreeding depression. Sometimes, however, the efforts to try and rescue imperiled populations result in outbreeding depression where maladapted alleles are introduced into the target population.
Pacific pocket mice have been extirpated from much of their historic range. Captive breeding at the San Diego Zoo was enacted to create a source population for reintroductions.- Whole genome sequencing of wild-caught as well as founding individuals was used to impute genotypes from other samples within the captive breeding program or part of wild populations
- There were differences across the three wild populations, with the smaller populations experiencing a greater genetic load and reduced heterozygosity.
- Museum samples from pre-coastal development revealed much higher historical heterozygosity in the smallest of the contemporary populations.
- The smallest population also contains additional chromosomes (2n=58) compared to the other wild populations (2N=56) resulting from a split of chromosome 2, which may reduce the efficacy of genetic rescue for this population.
- However, the captive-bred mice heterozygous for this chromosomal difference have more offspring and decreased genetic load compared to the wild population, suggesting that the benefits of gene flow outweigh the chances of negative effects due to the differences in chromosome number.
- Next steps include actually implementing genetic rescue in the wild population and measuring the fitness effects of reintroduced mice.
Anna Keyte, Barriers and potential for gene editing in avian conservation
Anna is a Species Director at Colossal Laboratory and Biosciences specializing in avian genome engineering. Colossal is the company working on de-extinction of the wolly mammoth, dodo, and Tasmanian tiger.
- For de-extinction, the template species is generally the next closest-related species (in the case of the dodo it’s the Nicobar pigeon).
- There is now a dodo, Nicobar pigeon, and Rodrigues Solitare (extinct) genome available as genetic resources.
- For birds, de-extinction is especially challenging because we cannot clone them like we can mammals.
- Therefore, a technology called primordial germ cell culture (where the gonads from a certain developmental stage is sampled and grown in culture to be placed in a host egg later) can be used to create cells for DNA editing. This has been successfully done in chickens but is still in development for other birds.
- This technology will first be tested for pink pigeons, which are still extant but critically endangered.
- Biobanking is a great resource for future genomic work in birds, but we should also include gonad tissue as well as somatic tissue because germline-restricted chromosomes are found in songbirds especially and generally the largest chromosome within the species.
Andrew Pask, Bringing back the past to protect the future: De-extinction of the Tasmanian Tiger
Andrew is the PI of the Thylacine Integrated Genomic Restoration Research (TIGRR) Lab at the University of Melbourne. Since European settlement, Australia has the highest global rate of mammal extinction. The TIGRR lab is hoping to reverse the extinction of Australia’s only apex predator, the thylacine.
- The de-extinction toolkit that is also beneficial for species conservation contains gene editing, assisted reproductive technologies, stem cell cloning, and tissue biobanking tissues.
- Bringing the thylacine back would help control the Tasmanian Devil’s devastating facial tumor disease as well as help reverse other ecosystem effects in Tasmania from the removal of its apex predator.
- Luckily, the Tasmanian ecosystem is mostly intact!
- Current genomic resources include a complete genome assembly, the first long-read RNA for an extinct species, and the first long-read methylation data for an extinct species.
- The next closest relative is the Dunnart, a chubby-tailed, mouse-size marsupial (fun fact, all marsupials are about 4mm in length when they are born), but there would still need to be 500,000-1,000,000 engineered changes to turn a dunnart into a thylacine
- Thylacines are extra cool because they have a lot of convergence with canids despite diverging ~170 million years ago. Most of the genetic convergence, however, lies in noncoding regions of the genome thought to be enhancers of genes
- one example is the Satb2 gene, which is really important in craniofacial development
- Conservation efforts of this work include the development of marsupial induced pluripotent stem cells (iPSCs), induction of increased ovulation rates in marsupials, and also the development of the first biobank in Australia
- This technology is also going to be used in the conservation of quolls to introduce a modification of the ATP1A1 gene to make them resistant to the toxin created by cane toads, an introduced species
Ana Velasquez-Escobar, Preservation of biodiversity through species-specific genetic biocontrol: Using gene drives to combat invasive mice
Ana is a graduate student in the Threadgill Lab at Texas A&M University. Her talk was selected from abstract submissions! Her work involves using gene drives to suppress invasive mice on islands as conservation measures
- Invasive rodents are especially harmful to island populations because many island species are endangered, rare, or vulnerable to biodiversity loss. Many endemic island species have been driven to extinction by rodent predation.
- Gene drive is an allele that transmits at much higher frequencies than expected under Mendelian segregation.
- Mice have a naturally occurring t-haplotype that, when carried by sperm, has a 95% chance of being conferred to the next generation. However, homozygotes are inviable.
- Transgenes can be created using plasmids as carriers and containing the modification of interest (in this case, a modified Sry gene) as well as antibiotic-resistant genes to confirm the success of gene transmission
- Transgenic mice containing these modifications are created and bred to confirm if the modification was successful, which is currently ongoing.